Multiplex radiophone communication system



April 14, 1953 J. H. HOMRIGHOUS 2,635,233

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April 14, 1953 J. H. HOMRIGHOUS 2,635,233

' MULTIPLEX RADIOPHONE COMMUNICATION SYSTEM Original Filed July 8, 1946 14 Sheets-Sheet l0 395 T0 FIG 2| FIG 20 INVENTOR.

April 14, 1953 J. H. HOMRIGHOUS MULTIPLEX RADIOPHONE COMMUNICATION SYSTEM Original Filed July 8, 1946 14 Sheets-Sheet l2 INVENTOR mmn April 14, 1953 J. H. HOMRIGHOUS MULTIPLEX RADIOFHONE COMMUNICATION SYSTEM 14 Sheets-Sheet 15 Original Filed July 8, 1946 mm @C INVENTOR.

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Km 0E Patented Apr. 14, 1953 MULTIPLEX RADIOPHONE COMMUNICA- TION SYSTEM John H. Homrighous, Oak Park, Ill.

Original application July 8, 1946, Serial No. 681,857. Divided and this application May 16, 1949, Serial No. 93,613

16 Claims. 1

This application is a division of application Serial No. 681,857 filed July 8, 1946.

This invention relates to a multiplex radio communication system and more particularly to a system for communication between mobile radio stations, and between mobile and fixed stations.

One of the main objects of my invention is to provide radio automatic relay or booster stations for extending a call over great geographical distances or beyond the horizon from a calling station.

Another object of my invention is to provide means for routing a call automatically through one or more fixed radio relay stations to a distant mobile radio station.

Another object of my invention is to provide means for routing a call automatically from a mobile radio station through one or more relay stations to any desired fixed radio station.

Another object is to provide means for routing a call automatically from a mobile radio station through one or more relay stations to any other mobile station.

Another object of the instant invention is to transmit like signals from all stations along a predetermined route simultaneously so that a mobile unit traveling the route may be in continuous communication with other mobile units or any fixed station.

Another object of my invention is to provide improved means whereby a plurality of messages or two-way conversations may be transmitted intermittently over a single transmission lane or carrier waves of the same frequencies.

Another object of my invention is to provide means in a radio communication system whereby any station may individually signal or call any mobile station regardless of the location of the mobile station along its predetermined route.

Another object of my invention is to provide means whereby the relative position of a mobile radio station along a predetermined route may be indicated at the mobile radio station.

Another object is the provision of means in a mobile station to indicate the relative location of all mobile craft traveling a predetermined route.

Another object of my invention is to provide means for indicating in the fixed radio stations at either terminal of an airway or mobile route or at fixed wayside stations the relative location or position and movement of mobile radio stations along the predetermined route.

Another object of my invention is to provide in a radio communication system means in the mobile and fixed radio stations to indicate when a communication channel is in use.

Another object of this invention is to transmit stations in different airplanes to indicate the altitude that the first airplane is flying.

Another object of my invention is to provide in a radio communication system means to transmit signals from fixed radio stations along a predetermined route to operate on course devices in the airplanes flying the route for indicating whether the airplane is on route.

Another object of my invention is to provide in a mobile radio communication system means at the fixed radio stations at either end of a predetermined route for transmitting the name of the city that the fixed station is located in or the name of the city that the airplane is flying toward so that a pilot flying the route may as desired listen to the route identification.

Another object is to provide improved means for routing a call from a mobile radio station through one or more fixed radio stations to a distant telephone orfice.

Another object is to provide means in an aircraft radio station for detecting received obstacle signals modulated on carrier waves of the same frequencies from a number of transmitters on top of buildings or mountains to thereafter determine the direction of any one of the transmitting stations relative the aircraft.

Message in this specification is to be understood to include any intelligence or any portion of any intelligence represented by sound, facsimile, code, or position indicating signals.

A channel in this specification is to be understood as a one way path for the transmission of electrical signals between distant stations, or a path for the transmission of signals during recurring periods of time, and may be one of a number of carrier Wave channels in a transmission path or lane for the transmission of signals representative of any intelligence and or control signals.

Messages may be transmitted through the common transmission path or lane in recurring periods. The preassigned periods of time for separate messages remain fixed regardless of the number of messages being intermittently transmitted.

Mobile stations referred to in this specification are to be understood as the radio transmitter and receiver stations located in an airplane, train, truck, bus, taxicab, boat, tank or any other Vehicle.

The multiplex radiophone communication system of the instant invention is applicable to many communication services by wireless transmission such as may be required for the operation of railroads, buses, trucks, taxicabs, airplanes, etc.

The radio transmitting and receiving stations are arranged to transmit message signals intermittently, or stated in another way, a message from one station may be transmitted intermittently during certain recurring periods of time, and a message from a second radio station may be transmitted during different recurring periods. No two signal originating stations in the same group may transmit signals during the same period of time. Likewise the receivers in each station may be arranged to receive signals only during certain predetermined periods.

The radio system shown and described herein is primarily for communication between fixed radio stations and mobile radio stations and comprises a plurality of fixed radio stations along a highway, railroad tracks, or an airplane route. lhe fixed radio stations may be spaced at certain distances along the conveyance route with terminal or transmitting and receiving stations at either end of the route. The intermediate radio relay stations may be used for relaying or retransmitting the signals to another relay or terminal station.

The communication systems described herein are intended for the transmission of message signals and the transmission of control signals for actuating mobile positions indicating devices, including altitude indicating devices and on course signals.

Mobile radio stations may be located in automobiles, trucks, buses, engine cabs, cabooses, airplanes or any other mobile vehicle. These mobile transmitter and receiver stations may through the radio relay stations communicate by speech, signaling or both with a fixed terminal station while traveling along a predetermined route.

Carrier waves of the same length may be employed for transmission of messages in both directions or carrier waves of the same length may be employed for communication west t east and other carriers of a different wave length may be employed for communication east to west.

This invention is an improvement over my prior patent, Number 2,369,783, issued February 20, 1945, which describes a television system for selecting a radio station by varying the transmitted signals, and also is an improvement over my prior applications. Serial No. 472,105, filed January 12, 1943, Patent 2,437,027, granted March 2, 1948, describes a communication system for the transmission and reception of several one way messages over a single channel, also application Serial No. 558,931, filed October 16, 1944, now Patent No. 2,532,719, granted December 12, 1950, describes a radi multiplex system whereby any station in a large group of stations including mobile stations may signal individually any other station in the group.

The synchronizing system employed for controlling the saw tooth generators may be an improvement over the method shown and described in my copending application Serial No. 476,897, filed February 24, 1943, now Patent No. 2,524,347, granted October 3, 1950, and Patent 2,398,641, issued April 16, 1946.

In the instant invention I may employ high or ultrahigh frequency carrier, frequency modulated; however, it is to be understood that the principles involved may be equally applicable to microwaves, and amplitude modulation may be utilized when desirable.

Other objects and advantages of my invention will appear from the following description taken in connection with the accompanying drawings in which:

Figures 1, 2 and 3 are diagrammatic illustrations of radio communication systems for airplanes, railroads, and highway vehicles; respectively.

Figures 4, 7, 9, 10, 12 and 14 are diagrammatic illustrations of numbering schemes for mobile multiplex radio communication systems.

Figure 5 is a diagrammatic illustration of the control signals.

Figures 6, 3 and 11 are diagrammatic illustrations of radio systems with signaling paths between stations for certain sections of the communication systems shown in Figures 1, 2 and 3.

Figure 13 shows an arrangement of radio stations along different routes.

Figure 15 shows a typical schematic'channel' arrangement between a number of stations.

Figure 16 and 17 are detail views of the transmitter and the receiver respectively employed inthe terminal and mobile stations shown in Figures 6, 8 and 11.

Figures 18 and 19 are detail views of. the receiver and the transmitter respectively employed in the relay and wayside stations in Figures 6, 8 and 11.

Figures 20 and 21 are circuit diagrams show-' ing the saw tooth" generators and channel control mechanism for transmitter receiver stations.

Figures 22 and 23 show details of the timing switches.

Figures 24, 25, 27, 28, 29 and 30 are detail circuit diagrams showing channel or period of time selectors employed in the several radio stations.

Figure 26 shows a cord circuit for connecting radio terminal circuits to telephone lines.

Figure 1 illustrates a radio communication system for several airplane routes comprising a terminal station in each large city and a number of radio relay stations spaced along the route. One or two transmission lanes or paths may be employed between terminal stations for two-way messages between the terminal stations and be tween either terminal station and the mobile stations in the aircraft proceeding along theairways. Carrier waves of the same length or of different length may be utilized for the transmission in either or both directions through therelay stations. Signals may be initiated in the mobile stations for sound communication and for actuating in each terminal station airplane position indicating and altitude indicating devices.

Figure 2 illustrates a radio communication system for railroads. This system may be similar to that described above for aircraft.

Figure 3 illustrates two separate communication systems along a highway, one for buses and another one for trucks. Other systems may be employed along the same route for communication with taxicabs, etc. Each of these systems may employ one or two transmission lanes, with two transmission lanes one would be used to transmit in one direction and the other lane or path would be used to transmit signals in the opposite directions. Furthermore, highway vehicle services probably would only be for the transmission of sound communication signals; however, if desired mobile position indicating devices may be employed. s r

I Figur 4 illustrates an arrangement or period of time fram for assigning and associating two digit numbers to a group of stations. This arrangement utilizes two saw tooth or timing waves; each wave may have ten frame divisions or parts. The waves are shown at right angles to each other to form a period of time or station number assignment frame. The horizontal waves may be ten times the frequency of the vertical waves so that the combination of the ten horizontal divisions and ten vertical divisions will give one hundred separate areas, or one hundred stations numbers. Smaller groups may be obtained by using only the horizontal saw tooth wave as described in my prior application Serial No. 558,931, and fewer divisions oi each wave may also be employed. Fifteen or twenty lines may also be employed in each frame.

While I have shown a system employing ten horizontal lines per frame, it is to be understood that there may be many horizontal lines for each horizontal portion or division of the frame. Figure 5 illustrates diagrammatically the horizontal or line, and the vertical or frame control signal for a group of stations as illustrated in Figure 4.

Figure 6 shows a plurality of radio stations along a conveyance route comprising a terminal or main station at either terminal of the route, a radio relay station and a wayside station intermediate the terminal stations, also three mobile radio stations are shown. This communication system may employ two carrier wave frequencies or two transmission lanes, one for transmitting signals from the east terminal toward the west terminal, and another carrier wave for transmitting signals from the west terminal toward the east terminal. One way communication may be over telephone trunks as illustrated. The transmitting antennas in the relay and wayside stations may have reflectors to shield the associated receiving antenna at the same station from signals radiated by the transmitting antenna. The radio relay stations in Figure 6 retransmit signals received from other stations. The mobile stations do not retransmit received signals.

Figure 7 shows a station numbering arrangement or station number assignment frame having longer periods than those in Figure 4 for the intermittent transmission of signals.

Figure 8 shows a radio communication system applicable to aircraft routes and other conveyance routes where it is desired to show in the terminal stations the relative locations of mobile equipment along the route and with airplanes the altitude at which each plane is flying. This system comprises a plurality of spaced radio stations along the route and a terminal station at both terminals of the route, and radio relay and a wayside station intermediate the terminal stations. The relay and wayside stations not only retransmit received signals but must produce signals in certain assigned periods under the control of mobile radio stations on the route, whereby, the relay stations or their control mobile station may be identified or shown on the position indicator at the terminal stations. Several mobile stations are shown, none of which retransmits received signals. This system employs two carrier frequencies, one for signals directed to the west terminal and a second carrier frequency for signals directed toward the east. The transmitting antennas/in the relay and wayside stations may have reflectors to prevent effective radiation back toward its associated receiving an tenna. One mobile station is shown with double transmitters and receivers to permit signaling in both directions simultaneously.

Figure 9 shows a station numbering scheme including mobile position indicating number arrangement and altitude indicating number arrangement for use in the communication system shown in Figure 8.

Figure 10 shows a modification of Figure 9 consisting of a larger group of mobile position indicating numbers to correspond to a. greater number of radio relay stations on a particular route.

Figure 11 shows another radio communication system utilizing only one carrier wave frequency for two way transmission between a terminal sta tion and mobile stations. In this system, if desired the terminal station may be provided with mobile position indicating devices similar to those in Figure 8. The terminal station may have considerable more power than the relay or mobile stations, necessitating more relay stations for the return channels.

Figure 12 shows a station numbering scheme for use in the communication system shown in Figure 11. The upper part of the number assignment frame represents station numbers for signal transmission toward the east while the lower part of the frame represents station numbers for signal transmission westward.

Figure 13 shows diagrammatically an arrangement of radio stations along routes running west to east and north to south so that the station numbers shown in the position indicating de vices are successively higher as the plane or mobile station moves toward the east or south.

Figure 14. is a typical period of time frame showing a channel numbering scheme fora number of different types of services for mobile and fixed radio communication stations, where much larger capacity is required to accommodate a large number of relay stations along a conveyance route. This frame also shows periods of time for transmitting facsimile signals for a number of mobile and fixed. stations, other periods for telephone messages and on course signals, to be explained later.

Figure 15 illustrates partial channel selector frames for a number of fixed stations and several mobile stations, with lines indicating certain channel paths between stations for the transmission of different messages in periodic rotation from a number of stations over carrier waves of the same length.

Figure 16 shows a block diagram for a transmitter in a transmitter receiver station that may be used in any of the terminal or mobile stations shown in Figures 6, 8 and 11. This transmitter comprises a number of selectors for selecting the proper timing impulses to control the intermittent transmission of signals for a number of different services such as facsimile messages, sound messages, operating position indicating and altitude indicating mechanisms.

Figure 17 shows a block diagram for a receiver associated with the transmitter of Figure 16. This receiver comprises a number of selectors for selecting the proper timing impulses or signals to control the intermittent reception of signals for a number oi different services.

Figure 18 shows a block diagram for a receiver in a relay or booster station that may be used in any of the relay or wayside stations shown in Figures 6, 8 and 11. This receiver comprises a number of selectors for selecting recurring periods under control of timing impulses for the reception of intermittent signals for several classes of services that are originated at other stations in the system.

Figure 19 shows a block diagram for the transmitter associated with the receiver in Figure 18. This transmitter comprises a number of selectors for selecting the proper recurring periods forretransmitting the signals supplied from the receiver of Figure 18. This transmitter when used in a relay station along an airplane route may transmit from a separate antenna on course signals to inform pilots when they are flying on the right side of the route.

Figures 20 and 21 show apparatus and associated circuits to produce two series of saw tooth timing waves to control the tens and units pulse generators or electronic timing switches. These switches may produce two series of timing impulses which may be employed by the several channel selectors in each station to control chan-- nel selection.

Figure 22 shows a detail view of the electrodes for the units timing switch.

Figure 23 shows a modified arrangement of the electrodes for the timing switch.

Figures 24 and 25 show apparatus and associated circuits for transmitter and receiver selectors respectively to select any one of a number of periods in successive saw tooth timing waves for the transmission of signals representative of diiferent messages such as facsimile, sound, the name of city on route and mobile position control signals.

Figure 26 shows a cord circuit for extending radio call to telephone lines.

Figure 27 shows apparatus and associated circuits for an altitude selector for mobile stations to select difierent periods of time under the control of an altimeter instrument for the transmission of signals representative of the altitude of the plane. Figures 28 and 29 show apparatus and associated circuits for position indicating selectors in the receiver and transmitter respectively forming a part of the relay or wayside stations. The selectors may select recurring periods for the transmission of signals representative of the particular mobile number and the number of the relay station to which a mobile station is signaling.

Figure 30 shows apparatus and associated circuits for an obstacle selector in mobile stations to select a group of channels for the reception of signals from a number of obstacle transmitting stations, and thereafter selecting any one channel for determining the direction of the obstacle transmitter relative the mobile station.

With further reference to Figure l which diagrammatically illustrates a radio communication system for airplane routes havin two transmis sion paths or lanes between terminal stations such as the terminal station 2! at Omaha and terminal station l2 at Chicago, station l2 and terminal station it at Detroit, and station i2 and terminal station is at Cleveland. Intermediate these terminal stations there may be a number of spaced radio relay stations for amplifying and retransmitting or relaying the signals along a predetermined route as illustrated by the reference numerals i5 through 18, 23, 24., etc. A wayside station where calls may be originated or answered is shown at 25. Aircraft 26 through 3! flying the several routes may be communicating through a relay station within the shortest distance of the plane over channels of the same wave length as shown by the connecting lines 32 through 36. There may also be carrier wave channels between the several airplanes as shown by the connecting lines 3'! and 38.

Referring to Figure 2 which diagrammatically illustrates a two channel radio communication system for railroads, one carrier wave channel may be for the transmission of message signals and train position indicating control signals west and a second carrier wave channel may be for the transmission of message signals and train position indicating control signals east. The terminal radio stations 39 through 42 may be separated by relatively large distance and at convenient locations for train dispatching services where it is desired to observe train movements along the tracks. Intermediate these terminal radio stations there may be a number of spaced radio relay stations it through 50 along the railroad tracks for amplifying and retransmit-ting the signals originated in the terminal stations or mobile sta-, tions and also for transmitting signals representative of its assigned number under the control of mobile stations in the several trains. A wayside station 5i, intermediate terminal stations 40 and H, may be provided for receiving and answering calls and also for observing train movements on the tracks between the terminal station through position indicating devices. Communication paths may be maintained between trains 52 and 53 moving along the double tracks and the terminal stations at both ends of the particular section of the railways through relay station within the shortest distance of either train as indicated by the connecting lines 54 through 51. Communication paths or channels may be employed between the mobile radio stations in the engine cab and caboose as illustrated by the connecting lines 53 and 59. Communication between moving trains may be over a carrier wave channel as illustrated by the line 6 3.

Referring to Figure 3 which diagrammatically illustrates two two-way radio communication systems for trucks and buses traveling a two-way street or highway. While I have shown only two types of vehicles, it is to be understood that other vehicles such as taxicabs may also have a separate-communication system along the same route. The two communication systems illustrated may be similar except that different carrier wave frequencies are used for the two systems and the several stations in each system may operate without interference from non associated stations.

The radio communication system for trucks may utilize two carrier wave transmission lanes, one for transmission west and another for transmission east. Fixed terminal radio stations 60 and 6! may be at either end of the route with fixed intermediate radio relay stations 63 through 61 spaced. along the predetermined route for retransmitting or relaying message signals to and from the terminal stations. Other radio relay stations not shown may be provided for greater distances between the radio terminal stations. Vehicle position indicating devices may be employed if desired as described above in connection with trains and airplanes, but it is thought that this type of service would not ordinarily be required for trucks, buses, etc. Communication channels may be maintained between trucks moving along the route in either direction through relay station within the shortest distance of the truck as shown by the lines 69 through ll. Communication channels may also be established between trucks as shown by the line 12.

The radio communication system for buses may be similar to that described for trucks. Two individual carrier wave transmission lanes may be provided, one for message signals transmitted west and another for message signals transmitted east. Terminal radio stations '33 and it may be provided at each terminal of the route with intermediate radio relay stations it through Bl spaced along the route for relaying message signals to and from the terminal stations. Other radio relay stations may be provided between terminal stations 73 and M. A wayside station t2 may be provided for originating and receiving message signals. Vehicle position indicating apparatus may be provided if desired as described above. Communication paths may be maintained for buses 83 and 85 as shown by the lines 85 and 86. Also communication channels may be established between buses fit and 81 as shown by the line 88.

While only a few airplanes, trains, trucks and buses are illustrated along the various routes, it is to be understood that the number shown does not represent the capacity of any of the communication systems, which will be more fully explained later.

With further reference to Figure 4, this figure illustrates a diagrammatic arrangement for assigning two digit numbers to a group of one hundred radio stations, and for allotting periods of time for the transmission and reception of message signals. In this arrangement I employ two series of saw tooth waves, one ten times the frequency of the other to select different periods of time for each station in the group. One saw tooth wave is shown vertically at 89 and the other saw tooth wave is shown horizontally at $53. By dividing each wave into ten parts as indicated by marks such as ill and 92 and assuming that the hori zontal frequency is ten times the vertical fre quency we would have ten equally spaced hori zontal lines in the frame diagram 88. An analogy to this is the scanning action over a cathode ray tube screen. Since each horizontal line is divided into ten equal spaces and there are ten lines in each frame, I may obtain one hundred imaginary areas for station number assignments or one hundred differentperiods of time per frame.

The location of each number in the frame may be considered as indicating the period of time that the assigned station may be capable of reproducing a message from received signals.

For an orderly arrangement of two digit station radiophone numbers, the first or tens digit of any number in the frame may be the number of the line counting from the top down and the unit digit is the space in the line counting from left to right; thus the radiophone number 94 is in line nine, space four as shown. The number 09 is bottom line space nine. It is not necessary to assign radiophone numbers as outlined above, but any number may be assigned to any period in the frame as desired.

It'is to be understood that small groups of stations may be employed in any of the communication systems described herein by employing only the horizontal series of saw tooth waves.

Line and frame control signals or impulses as illustrated at 85 and 96 are transmitted at regular recurring periods between stations to control the development of line and frame or horizontal and vertical saw tooth waves.

With further reference to Figure 5, I have shown diagrammatically line and frame control signals for controlling or timing the development of saw tooth waves for the group of stations in any of the radio communications systems described above. The horizontal or line control signals 95 are equally spaced. The frame or vertical control signal 36 is of greater amplitude and appears between groups of line control signals. These control signals or impulses are for synchronizing the saw tooth timing waves at the several stations. The horizontal and vertical control signals may be of equal amplitude as shown in application Serial No. 542,317 filed June 27, 1944, now Patent No. 2,521,008, granted September 5, 1950.

With further reference to Figure 6 which diagrammatically illustrates a two transmission lane radio communication system along a conveyance route intended for the transmission of sound message signals and control signals. This communication system may represent the radio communication system for buses described in connection with Figure 3 and the radio stations have been so numbered. Although all the stations in Figure 3 have not been shown, it is to be understood that any number of automatic radio relay stations, such as 16 may be employed between terminal stations 13 and 1d. Terminal station 13 may signal the wayside station 32 or the terminal station M over carrier waves of the same frequency through the automatic radio relay station 15. Terminal radio station M may signal station 73 over a carrier wave having a different frequency through stations 82 and it. The two terminal stations '53 and it may be similar. Each terminal station comprises a transmitter dl, saw tooth generators and channel control mechanisms, 98, and a receiver 99. The transmitter 9'! may transmit signals intermittently for signaling a called station or in other words signals from station 13 may be transmitted during certain reoccurring periods. Likewise the receivers 99 may be arranged to reproduce the received signals only during certain predetermined periods. The generator and mechanism 93 comprise saw tooth generators with apparatus and suitable circuits to produce timing impulses for controlling signal transmission and reception. Synchronizing signals may be produced in one station and transmitted to all other stations to synchronize the saw tooth generators.

The saw tooth waves shown in Figure 4 may illustrate one line saw tooth wave and one frame saw tooth wave of two series that may be produced in either terminal station, the Wayside station 82 and the mobile stations 83, i l and 81 for allotting periods of time for the tranmission and reception of signals.

The terminal stations (3 and 14 may be provided with a microphone and speaker I66) and It! adapted to be disconnected by insertion of the plugs in the cord circuits M32. The cords it? may extend the radio channel through telephone line apparatus at Hi3 and I04 to subscribers stations or trunk lines to the telephone oiiice I05.

The mobile stations and the wayside station 82 may be similar. Since these stations may be required to transmit on both carrier waves simultaneously each station 82 and 84 may comprise two transmitters lilii and H31, two receivers Hi3 and H99, and saw tooth generators and channel control mechanism lit. Each of the transmitters I66 and It? may transmit message and control signals during intermittent periods. The

estates 11 receivers IE8 and it!) may be arranged for the reception of signals during certain periods. The generator and channel mechanism its in each station are similar to the generator and mechanism 93 described above.

Station 84 may also be considered as a portable relay station which may be used to replace another station such as 82 in case of an emergency or it may be used to extend the communication route.

' The wayside station 82 may be equipped with a microphone and speaker ill for communication east or west through switch H2.

The automatic radio relay station in may comprise two amplifiers II3 and M4 to amplify and retransmit received signals without demodulation and remodulation.

Reflectors i l5 may be provided for each transmitter antenna in the relay and the wayside stations to prevent radiation to their associated receiving antennas.

Mobile stations 83 and 8? may be similar to terminal stations 73 and i l except that they are provided with adjustable tuning switches lit.

The mobile radio stations may be provided with lower output power because they may transmit signals over less distance than the fixed stations.

In Figure 6 I have illustrated two transmission lanes A for transmitting east, and B for transmitting west, also a terminal station at either end of the route. In the operation of truck fleets, bus fleets, etc., it may only be necessary to have one main dispatching or terminal station, therefore the wayside station 82 and terminal station i l may be omitted.

Figure '7 illustrates diagrammatically the signaling periods and radiophone numbers for the mobile, wayside and terminal stations in one of a series of frames which may be produced in Figure 6. The number assigned to the periods or channels may be the station numbers shown in Figures 3 and 6. The periods alloted to signaling may be varied to suit operating conditions. This numbering arrangement may apply to both transmission lanes A and B. The horizontal saw tooth timing wave frequency may be twice or four times the vertical saw tooth timing wave frequency.

While I have described the radiophone system in Figures 6 and '7 as applied to the communica-' tion system as shown in Figure 3, it is to be understood that this system is equally applicable to the communication systems for Figures 1 and 2 where mobile position indicating and altitude indicating devices are not desired.

Each station in the communication system shown in Figure 6 including the mobile stations may have a number which is assigned to a particular area in the time frame or a definite pe riod developed by the saw tooth timing waves as shown in Figure '7. This numberedperiod may be associated with the station call channel or path. It is to be understood that for a few stations only the line saw tooth timing wave generator would be employed.

Station i3 may call station it by selection of the proper period of time in successive saw tooth waves to transmit signals and thereafter the calling party may talk to the called party at station is informing the called party that station i3 is calling, whereupon the called party to communicate with the calling party will adjust the channel selector in his transmitter to select the call number or channel it to transmit signals during recurring periods. Saying it differently, each station is assigned a call channel which is associated with his station radiophone number, and for two-way conversation between two stations both station channels would be employed with each station transmitting signals over a selected channel and V receiving signals over its assigned call channel.

At the same time that the parties at the terminal stations are talking, other talking channels may be established between mobile stations going in the same direction or traveling in opp'o site directions. The mobile station channels may be direct from one station to another station when the distance between them is relatively short. But channels may be through the relay and wayside stations where the distance between two stations is relatively great. Mobile station to communicate with either terminal sta-- tion may transmit on one frequency and receive signals on a different frequency, therefore, a mobile station calling another mobile station over a short distance may through the operation of panel switches I I5 transmit on a different frequency than the called station. The two terminal stations 13 and i4 transmit on different frequencies.

The wayside station 82 comprises two transmitters and two receivers for demodulating and remoclulating signals in the two transmission lanes A and B. This wayside station may be located in an area without regular telephone service and calls may be made from this station to either terminal station through the operation of switch I !2. At the terminal stations. connections may be made to telephone lines.

Either of the mobile stations 83 or 81 may be considered as portable for maintenance crews, or they may be considered as fixed station in some isolated community where they may be employed to establish private communication paths to distant telephone oifices without interfering with or overlapping of signals in the regular communication lane.

In station '53 certain of the signals received over the transmission lane B may be retransmitted over carrier wave channels in the transmission lane A so that all mobile stations may transmit over 13 and receive signals over A in order that one mobile station may signal and talk to any other. mobile station in the system without searching to find out whether the called mobile station is east or west of the called station, to be more fully explained later.

With further reference to Figure 8 which diagrammatically illustrates another two carrier radio communication system along a conveyance route intended for the transmission of message signals, including control and other signals for operating mobile position indicating devices. This communication system may be considered as a modification of the system shown in Figure 6, which modification comprises primarily the features of indicating or showing at the terminal and mobile stations the relative position of the mobile stations moving along the route, also 'on course signals where desirable with aircraft. This communication system may represent the communication system for airplanes and trains described in connection with Figures 1 and 2 and the radio stations I2, 23, 2 3, 25 and M are the stations having similar numbers in Figure 1 and may also be considered as stations '46, 46, '41, 5| and ll in Figure 2. Although all the stations in either Figure 1 or 2 have not been shown, it is to be understood that any number of automatic radio relay stations or booster station's such as 23 

